Egnine running away with itself - solved + some questions

tombardier · Mar 30, 2009

Greetings there,

re. 2.5na 1988 lr90

Yesterday we were driving to a friends house about 10 miles away. and just as we went over a motorway bridge on a sharp bend, the engine started running away with itself, and carried on, just revving as much as it possibly could! I read a thread on here the other day where someone was saying this could be due to a knackered seal, and the engine might be running on its own oil... My stomach sank so low I felt sick haha... It turns out, it'd run out of diesel.. I don't know why this would happen though? It was certainly fine after pumping some diesel in there. I just wonder how that works.. If ever someone has the same problem, just check that hehe.

It doesn't help that my fuel tank always seems to indicate that it's half full. I noticed that there are three pairs of wires going in to the fuel tank, and wonder if maybe one of them's knackered? They just sit on top of the chassis. If there's any tips on fixing the guage without cracking the tank open, that'd be much appreciated

Cheers. Tom.

ratty · Mar 30, 2009

tombardier said:
Greetings there,

re. 2.5na 1988 lr90

Yesterday we were driving to a friends house about 10 miles away. and just as we went over a motorway bridge on a sharp bend, the engine started running away with itself, and carried on, just revving as much as it possibly could! I read a thread on here the other day where someone was saying this could be due to a knackered seal, and the engine might be running on its own oil... My stomach sank so low I felt sick haha... It turns out, it'd run out of diesel.. I don't know why this would happen though? It was certainly fine after pumping some diesel in there. I just wonder how that works.. If ever someone has the same problem, just check that hehe.

It doesn't help that my fuel tank always seems to indicate that it's half full. I noticed that there are three pairs of wires going in to the fuel tank, and wonder if maybe one of them's knackered? They just sit on top of the chassis. If there's any tips on fixing the guage without cracking the tank open, that'd be much appreciated

Cheers. Tom.

I don't wanna worrry you Tom but I've never known an engine to run on when it runs out of fuel.

wiltshire landyman · Mar 30, 2009

try a new fuel sender unit...or first remove connections on top of the tank sender unit and clean them and all the contact points and see if it makes any difference

tombardier · Mar 30, 2009

ok. but it definitely had run out of fuel. I had to reprime the system after trying to start it up a few times and failing, and I could hear the hollowness of the tank as I poured more in it. When I primed it with the mechanical pump, it started up after turning over a number of times, and it went straight to its normal purr..

wiltshire landyman. Is the fuel sender unit actually just on top of the tank?

Cheers. Tom.

wiltshire landyman · Mar 30, 2009

yeh under drivers seat,they usually get full o mud n ****e.worth a try

Shifty1962 · Mar 30, 2009

If you'd run out of diesel then the engine must have been running on something else.
The only candidates are sump oil or fresh air and I know what my money is on.
If you can get a diesel engine to run on fresh air then you'll be a very rich man or the oil companies will bump you off one dark night.

tombardier · Mar 30, 2009

My friend, the one I was visiting, he knows a lot about motorcycle engines. . Enough to rebuild them blindfolded, but he doesn't know anything about diesel engines. He thought it could be explained by there being too much air in the system shortly before it ran out of the system completely.. I don't pretend to know enough about it, but it sounded plausible enough to stop me throwing up with the worry!... so maybe it _was_ running on fresh air, or pressurised diesel vapours?!

If it was running on sump oil, I could expect to see plumes of smoke no? There wasn't any of that.. Once it started going again, I had the normal big puffs of grey smoke, and then no visible smoke..

Still a mystery!

The Mad Hat Man · Mar 30, 2009

whatever it was, or is - I suggest you remember Patmans trick in case it does it again.

ratty · Mar 30, 2009

The Mad Hat Man said:
whatever it was, or is - I suggest you remember Patmans trick in case it does it again.

And put 999 on speed dial.

tombardier · Mar 30, 2009

Sorry, but I'm still quite green on the forums

Patman's trick?

boydy1989 · Mar 30, 2009

with a botormike it will run faster as it runs out, 'cos as the cabs empty of fuel it can't suck in as much fuel, so it runs leaner and therefore faster.

on a doosel i can't think why this would be, unless some crap from the tank jammed the governer

The Mad Hat Man · Mar 30, 2009

tombardier said:
Sorry, but I'm still quite green on the forums

Patman's trick?

yup - if it starts to run away - DO NOT press the clutch - put yo foot on the brake hard and stall the engine in as high a gear as you can.

tombardier · Mar 30, 2009

dirt in the tank jamming the governor? might be getting somewhere hehe.. The crap I got out of the tray at the bottom of the fuel filter was nice a week or two ago. Quite a bit of grit and crap. so it wouldn't surprise me if there was **** in the tank. At least I know there's no red diesel in the tank any more anyway (from the farmer I bought it from)

boydy1989 · Mar 30, 2009

it shouldn't have got past the fuel filter, but if your fuel filter status is unknown, it may well have dis in teg rated, meaning some crap got into it.

THat said, it sounds pretty unlikely to me.

tombardier · Mar 30, 2009

Right, I just looked at my workshop manual, and in the "fault finding:engine will not idle" section, for diesel engines in particular, it says "air in fuel", so it doesn't sound so unlikely

I guess it could be running rich in the same way as a petrol engine?

tombardier · Mar 30, 2009

or that section's probably for the engine cutting out because it won't idle high enough :/

tombardier · Mar 30, 2009

and i changed the fuel filter for a new one by the way. new seals too, and it's nice and tight. no leaks or anything.

slim jim · Mar 30, 2009

I spent 12 months convincing myself that it wasnt a head gasket problem.Just when I was sure that I was right the head gasket went

lerk · Mar 30, 2009

Normally a petrol engine will only "rev up" as it runs out when ticking over, as soon as you move off the pilot jets the fuel isn't available for the extra air, so most running out = very quick stop of the engine, not increasing revs...

tombardier · Mar 30, 2009

you had the same issue? Did it happen often, or when the engine was hot perhaps?

Egnine running away with itself - solved + some questions

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